The invention concerns a device for the capacitive level measuring of a liquid in a container in which two electrodes are positioned in the container and extend above the filled level area of the container. The two electrodes form a measuring condenser in which the capacitance varies according to the level (filled state) of the fluid. One of the electrodes is divided along its height into two partial surfaces which are insulated from one another to form two partial capacitors.
Usually, in the capacitance measurement of the level of a fluid, the dielectric susceptibility K of the filling medium is assumed to be constant. That is, it is assumed to be the average value over the work temperature range and the spectrum of the K values of all fill mediums to be processed. The indicator for measuring the capacitance is then set to this average value. Frequently however the susceptibility values of the fill mediums to be measured are so far apart that a measurement with the aid of the average value is no longer possible, or is imprecise. A reference condenser has been used in the past for measurements of mediums with rather large variations of the K values. This reference condenser is constantly in contact with the mediums and must be positioned, for example, at the lowest position of the container to be able to guarantee the reference measurement even at low levels of filling.
The disadvantage of this method is that the comparison condenser is subject to increased stress due to dirtying and corrosion which results in instances where unfavorable values for the conductibility and dielectric susceptibility are measured at the location of the reference condenser. These unfavorable readings may significantly deviate from the rest of the container contents.
Accordingly, it would be advantageous to provide a means for capacitively measuring the level of a fill medium in a container in which the variable dielectric susceptibility of the fill medium is considered, and where separate conclusions concerning the level and the susceptibility of the medium can be made.